Vehicle control system

ABSTRACT

A vehicle control system for supplying vehicle control data or other communicative data to a plurality of vehicles which are constrained to transit a predetermined network of travel paths. An array of twin lead conductors are disposed beneath the surface of the travel paths and form a distributed antenna network. Vehicles passing along the transit paths are equipped with transmitting apparatus which uses the antenna network as a communicative medium for providing two way communication between a stationary control unit and the vehicle carried mobile control units. An array of single conductors is also disposed along the travel paths and are energized with a low frequency AC signal for developing magnetic fields which are detected by a vehicle carried guidance control unit for guiding the vehicle along a particular path.

limited States Patent 1191 Comer 1 May 22, 1973 54] VEHICLE CONTROLSYSTEM 3,610,363 10 1971 Hartley ..1so 9s [75] Inventor. Donald T.Comer, Los Gatos, Calif. Primary Examiner Kenneth H. Beds [73] Assignee:Mobility Systems, Inc., Santa Clara, Attorney-Lowhurst & Hamrick Calif.22 Filed: Apr. 11, 1969 [57] ABSTRACT A vehicle control system forsupplying vehicle control [21] Appl' 8l5467 data or other communicativedata to a plurality of vehicles which are constrained to transit apredeter- [52] US. Cl. ..180/98, 340/32, 246/8 mined network of travelpaths. An array of twin lead [51] Int. Cl. ..B62d 5/04 conductors aredisposed beneath the surface of the [58] Field of Search ..340/32;325/26, 28, travel paths and form a distributed antenna network. 325/23,117, 312, 314; 180/98; 246/2-5, 8 Vehicles passing along the transitpaths are equipped with transmitting apparatus which uses the antenna[56] References Cited network as a communicative medium for providingtwo way communication between a stationary control UNITED STATES PATENTSunit and the vehicle carried mobile control units. An 2,255,055 9 1941Halstead ..340 32 array of Single conductors is also disposed along the2,429,607 0 947 Cape 3 0 32 travel paths and are energized with a lowfrequency 2,661,070 12/1953 Ferrill ..340/195 AC signal for developingmagnetic fields which are de- 2,980,793 4/1961 Daniel ..340/32 tected bya vehicle carried guidance control unit for 3, 05, 9 9/1963 y guidingthe vehicle along a particular path. 3,147,817 9/1964 Deliban.........l80/98 3,512,601 5/ 1970 Wilson .z ..180/98 4 Claims, 3 DrawingFigures WAREHOUSE CONTROL UNIT TO COM PUTER COMM 28 SYS COMM SYS GUID,CONT VEHICLE CONTROL SYSTEM BACKGROUND OF THE INVENTION Field of theInvention The present invention relates generally to vehicle controlsystems and more particularly to a system using magnetic energy toguide, and electro-magnetic energy to communicate with one or morevehicles which are caused to transit a network of travel paths.

Systems for providing communication between a moving vehicle and a basestation have long been known in the prior art. Now in widespread use arethe systems wherein a transceiver is carried on board a vehicle forenabling communication with a base station, relay station or othervehicle similarly equipped, via radio waves passed through theatmosphere. These systems have now been perfected to the point of nearideal utility for most types of communicative uses except where largemetallic obstacles may provide substantial interference with the path ofcommunication.

In applications where there are physical impedances to the communicationpath, or the distance over which the communication is to be practicedexceeds the practical or authorized range, a given transmitting station,a plurality of relaying stations (and/or receivers) may be suitablyspaced apart to circumvent the obstruction or extend the communicationpath. In railroad communication systems, for example, a plurality ofrelay stations may be spaced along a given railway route to facilitatethe transmission of data or voice communication between one or moretrains and one or more base stations.

Communication systems of this type have also been used for guidancepurposes to control unmanned vehicles, but have suffered from a generallack of dependability in environments where the path of transmission isor may be interfered with by radio impervious or radio reflectivestructures either natural or man-made. It has been found impractical,for example, in the case of remote controlled warehouse vehicles toattempt to transmit radio control information to a receiver on board awarehouse vehicle from a central antenna structure mounted near the roofof the warehouse because of the interferences produced by the buildingsuperstructure as well as metallic bins and other obstructions withinthe warehouse.

Modern warehousing principles now demand that a practicalintercommunication system be provided for transmitting computerizedcontrol data to and from a warehouse vehicle with complete reliability.Such a system is a necessary corequisite to the practical application ofautomated vehicle guidance systems which are now being used in thewarehousing industry. A guidance system wherein one or more warehousingvehicles can be controlled to follow predetermined transit paths isdisclosed in the copending US. Pat. application Ser. No. 698,217 filedJan. 16, 1968, now Pat. No. 3,507,349 and assigned to the assignee ofthe present invention.

Objects of the Present Invention It is therefore a principal object ofthe present invention to provide a vehicle control system in which aplurality of automated or semi-automated vehicles are simultaneouslycontrolled from one or more stationary control stations.

Another object of the present invention is to provide a vehicle controlsystem including a low power radio communication system which is notsubject to transmission interferences normally encountered in prior artvehicle intercommunication systems.

Still another object of the present invention is to provide a vehiclecontrol system including a communication system for supplying electroniccontrol data to a plurality of warehouse vehicles or the like, which ishighly reliable and will not cause radio interference with othertransmission systems in the vicinity.

Still another object of the present invention is to provide a vehicularcommunication system including a distributed antenna network which isarrayed to coincide with the paths of travel of one or more controllablevehicles.

Summary of the Invention Briefly, the present invention includes aguidance conductor disposed along one or more vehicle paths fordeveloping magnetic guidance fields, a transmission line disposed alongthe vehicle path, a stationary control unit coupled to the transmissionline and a mobile control unit which uses the magnetic guidance field asa means of guiding the vehicle along the vehicle paths, and throughelectro-magnetic induction, uses the transmission line as a means ofcommunicating control data and response data to the stationary controlunit.

In accordance with the present invention, any number of vehicular unitscan be simultaneously controlled from a stationary central controlstation and can transmit back thereto any requested verifying data orother communicative information.

A principal advantage of the present invention is that due to theinherent nature of the disclosed distributed antenna system, thecommunicative data radiated therefrom is substantially limited to thepaths over which the intended receiving vehicles are to pass.

Another advantage of the present invention is that since the radiationfrom the distributed antenna array is localized within the vehicularthoroughfares it can be received through antenna structuresappropriately mounted on the vehicles and carried at short distancesfrom the array so that the transmission path is, under normalconditions, never subject to interference.

Still other advantages of the present invention will become apparent tothose skilled in the art after having read the following disclosure ofpreferred embodi ments, which are illustrated in the several figures ofthe drawing.

IN THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now toFIG. 1 of the drawing, an illustrative example of a warehouse layout isshown including guidance and communication means for directing andcontrolling one or more warehousing vehicles. The schematic illustrationdepicts a basic warehousing floor arrangement wherein a plurality ofbins are disposed in spaced apart relation to form a plurality of binrows and columns with main aisles 12, 14 and 16 and bin aisles 18through 28 for allowing access to the respective bins.

Disposed within the floor of the various aisles, and beneath the pathsto be followed by the warehousing vehicles illustrated at 30 and 32, isa first guidance conductor 34 for developing a magnetic field thereaboutfor use in providing vehicle guidance in the main aisles 12, 14 and 16,a second guidance conductor 36 for developing a magnetic fieldthereabout which is used to provide vehicle guidance through the leftbay of bin aisles 18 through 28, and a third guidance conductor 38 fordeveloping a magnetic field thereabouts which is used to provide vehicleguidance through the right bay of bin aisles 18 through 28.

Each of the guidance conductors 34, 36, and 38 are energized withguidance signals developed by the guidance cable driver 40. The guidancesignals are typically low frequency AC signals of frequencies F(a), F(b)and F(C) respectively. With the conductors 34, 36, and 38 so energized,a time varying magnetic guidance field is created about the respectiveconductors which can be sensed by suitable magnetic detection apparatuscomprising a part of the guidance control means 42 carried on board thewarehouse vehicles. A preferred form of such a guidance means isdisclosed in the previously referred to US. Pat. application Ser. No.698,217.

in accordance with the guidance system illustrated in the presentdrawing, which may be considered as extension of that illustrated in theaforementioned copending applications, a vehicle can be electricallycaused to direct itself to any desired position adjacent any of the bins10 for enabling extraction or deposition of any articles, stored or tobe stored therein in the respective bins 10.

Because of the differences in frequency of the signals used in mainaisle guidance conductors 34 and the bin aisle guidance conductors 36and 38, frequency selective circuits in the guidance control means 42 inthe vehicle control unit can be used to develop control signals fordiverting the vehicle from the main aisles 12, 14, or 16 to any of thebin aisles 18 through 28 and visa versa. This may be accomplished in ahighly accurate efficient manner by the method and apparatus disclosedin the above mentioned copending application.

Although it is also possible to supply control data to the vehiclesthrough modulation of the guidance conductors, this has been found to bean unsuitable method for a multi-vehicle system because of the limitedinformation rate which can be achieved by modulating a low frequencycarrier (the guidance signal).

In accordance with the present invention, an array of twin leadconductors is provided beneath the intended path of the warehousevehicles for conducting low power communications signals developed by awarehouse control unit (WCU) 58. These signals cause lower powerelectromagnetic communication fields to be developed in the immediatevicinity of the c0nductors which can be detected by suitable receivermeans forming a part of the vehicle units (VCU) carried on board therespective vehicles. Once detected, the control signals can then be usedto cause the vehicle to procede to selected positions within thewarehouse and to perform any number of desired functions. As illustratedin FIG. 1, a trunk line 44 is extended extended along the bin aisle 18past main aisles 12 and 14, and then turned to continue down the mainaisle 16 where it is terminated. At point 46 a suitable transmissionline splitter is provided for coupling a line 51 to trunk line 44. Line51 extends down the main aisle 12. Similarly, a second splitter is usedat 50 to couple a line 52 to line 44. Line 52 extends down main aisle14. In order to provide transmission lines in each of the bin aisles 20through 28, a plurality of branch lines 54 and 56 are splitter-coupledto line 52 and extended along the respective bin aisles as indicated.

These transmission lines are, in a preferred form, high quality twinlead plastic jacketed conductors which are terminated at their distalends in suitable impedances. In this form the array of interconnectedtwin lead transmission lines form a distributed antenna system whichpermits intercommunication between the warehouse control unit 58 and thevehicles 30 and 32. When energized with communication signals,transmission line 44 develops an electro-magnetic communication fieldwhich can be detected by a suitable electromagnetic energy sensingdevice. The respective sections of transmission line are typicallyintegrated within the concrete or asphalt floor slab of a givenwarehouse during initial construction or are provided in grooves orchannels subsequently cut therein which may be subsequently filled tofloor level to provide a smooth floor surface.

In one embodiment, such as illustrated in FIG. 2, the twin leadtransmission line 44 is disposed in the same channel or groove 62 cut inthe floor 64 which is occupied by the guidance line conductor 34. Oncethe conductors 34 and 44 have been suitably positioned within thechannel 62, the channel is filled with a suitable filler material 68 toprovide a smooth warehouse floor with the conductors concealed therein.

The controlled vehicles 30 and 32 carry suitable antenna or otherelectro-magnetic energy sensing devices 88 and which are positioned nearthe floor 64 for sensing the energy radiated from the conductors 34 and44. The antenna 90, for example, is coupled to the guidance controlmeans 42 and is capable of sensing the magnetic guidance field createdaround the guidance cable 34 so that vehicle 30 may be caused to followa selected path. The antenna 88 is positioned to receiveelectro-magnetic energy radiated from the twin lead conductor 44 inresponse to the communicative data transmitted by the warehouse controlunit 58. Similarly the antenna 88 can be used to radiate communicativeenergy back into the line 44 for sending return information to thewarehouse control unit.

Turning now to FIG. 3 of the drawing, a more detailed block diagram isprovided to schematically illustrate certain operative components of thepresent invention. Like members in FIGS. 1, 2 and 3 refer to likecomponents. As was illustrated more generally in FIG. 1, the warehousecontrol unit 58, which is responsive to a computer input at 70, iscoupled to the transmission line 44 which is in turn coupled throughsplitters 74 into branches which extend along the various aisles of thewarehouse. The warehouse vehicles 30 and 32 (FIG. 1) each carry avehicle control unit 86 which is communicatively coupled to thewarehouse control unit through the transmission line 44.

Also extending along side the transmission lines 44, etc., and withinthe same aisles are guidance lines conductors 34 which are energized bythe guidance cable driver 40. The guidance field created aroundconductor 34 is detected by the antenna 90 which in turn develops anelectrical signal to which the guidance control system responds todevelop appropriate control signals for guiding the vehicle along aselected path. Warehouse control unit (WCU) 58 includes an inputoutputinterface 92, control logic 94, a modulator 96, an rf transmitter 98, aswitch 116, an rf receiver 112 and a demodulator 114, all of which areof conventional construction.

In general, the WCU 58 has three main functions. First, it usesinterface 92 for coupling certain control logic 94 to the input/output(I/O) channel of a computer. This gives the WCU the ability to exchangedigital information directly with the computer. In this respect, the WCUresembles any other [/0 device connected to a computer.

Secondly, by means of control logic 94, it stores and shifts digitalinformation transmitted to and from one or more vehicles, regulates thetiming and data rates of transmitted and received information, anddecodes appropriate digital words received from the computer orvehicles.

The third function of the WCU is the actual RF transmission andreception of information. RF transmission of data by the WCU may beaccomplished in the following manner: The external computer sends agiven input command signal in the form of one or more digital (binary)words to the WCU 58. The binary words, after receipt by interface 92,are passed to control logic 94 for storage in a data register whichpermits a later checking operation and are simultaneously placed in aserial shift register. The control logic 94 then shifts the data out ofthe serial shift register into modulator 96 and RF transmitter 98 in aserial mode.

An RF signal is then modulated in modulator 96 by the binary value ofthe highest order signal in the shift register and is thence transmittedover the terminated RF transmission line 44 which is arrayed in thefloor throughout the warehouse as illustrated in FIG. 1. It should benoted that the system is not restricted to a serial mode oftransmission. The serial mode is merely chosen as being preferredbecause of the smaller band width required and the smaller degree ofcomplexity required for modulation.

As was mentioned above, the transmission line 44, is utilized as adistributed antenna which runs throughout the warehouse and parallelsthe possible paths of the mobile vehicles under guidance control by theguidance control system 42. Since the transmission line 44 is terminatedin its characteristicimpedance, there is little radiation a few feetaway from the transmission line. However, signals picked up a few inchesfrom the line will be much greater than normally required for an RFreceiver. By utilizing an automatic gain control circuit in the systemreceivers, it has been found that the vehicle antenna can actually beseparated from the transmission line by as much as three feet withoutinterruption of communication.

Each of the vehicles 30 and 32 respectively is equipped with an antenna88 which is typically mounted near the floor and in a position whichwill follow the locus of the transmission line 44 as closely aspossible. In a preferred design the vehicle antenna 88 is never allowedto stray more than a few inches from the transmission line so that thesignal picked up thereby has a relatively high signal-to-noise ratio.This signal is amplified and demodulated in the receiver and demodulator102 respectively, of the vehicle control unit 36 and is then loaded intoa data register of the control logic 104. Control logic 104 includessuitable conventional logic circuits and registers which respond to thecommunication signals input thereto via demodulator 102 and generateappropriate function control signals for driving the function controlmeans 105 as well as developing guidance selection signals for input toguidance control means 42. The function control means schematicallyrepresented by block 105 include any of the various mechanical,electro-mechanical or other means required to carry out the intendedoperative functions of the vehicle. Normal error checking schemes suchas parity checking, etc., may be used to insure the accuracy of thereceived data.

Since accuracy is of utmost importance, a retransmit/verify scheme ispreferably employed in the system. In accordance with this scheme, oncethe VCU receives a signal, the vehicle transmits the same data back tothe WCU for comparison. This is accomplished by use of the modulator 106and RF transmitter 108 which are connected through the switch 110 to thevehicle antenna 88 the couple the transmitted energy back into thetransmission line 44 for transmission back to the WCU 58.

The RF receiver 112 and demodulator 114 are opened to the transmissionline 44 by the switch 116 to allow the retransmitted data to reach thecontrol logic 94. If the data word does not compare bit by bit with theword originally sent by the WCU, then a check character is transmittedto the vehicle control unit 86 followed by re-transmission of theoriginal data word. This insures the correct transmission of data to thevehicle control unit 86 and gives the computer a means of identifyingfaulty operation of a vehicle control unit.

Transmission of data from the control unit of vehicle 30 is accomplishedin substantially the same manner as from the WCU except that the data isinductively coupled into transmission line 44. More specifically, an RFsignal is developed in modulator 106 by the digital word to betransmitted and the word is fed out of control logic 104 in a serialmode to the vehicle antenna 88. Since the vehicle antenna is typicallyclose to both the transmission line 44 and guidance conductor 34 eitherline could be employed as the return transmission medium to the receiver112 of the warehouse control unit 58 but it is preferrable that line 44be utilized. It should also be understood that as an alternative to thebalanced termination of the transmission line 44, the remote end thereofcould be returned directly to the receiver 112.

In the proposed system, data transmitted from the WCU 58 is intended fora particular vehicle alone. In order to accomplish segregation of thetransmitted signals to the various vehicles, each vehicle is assigned anidentification number (ID) such that when data is to be transmitted to aparticular vehicle the WCU first transmitts the desired vehicle ID code.In accordance with retransmit-verify feature of the system, the vehiclewill then transmit its own ID code back to the WCU. Upon receipt of theproper ID, the WCU is then assured that the proper vehicle is receivingthe data. A given vehicle cannot use any of the data transmitted overthe transmission line and will not retransmit data unless its particularID code has first been received and properly decoded.

When the WCU has finished transmitting data to a particular vehicle, thelast word sent to the vehicle is an end of transmission (EOT) character.This character resets the decoder of the vehicle ID section (in controllogic 104) and the vehicle will not accept further data from the WCUuntil its ID code is again received.

To eliminate interference from different vehicles transmitting data tothe WCU, a particular vehicle is allowed to transmit back to the WCUonly immediately after the WCU has transmitted data to that vehicle,i.e., following receipt of the EOT character. The vehicle, therefore,will transmit data from the retransmitverify operation only when it hasproperly decoded its ID code. In addition, the vehicle may transmit newdata such as status conditions to the WCU only after the WCU hasfinished a transmission to that vehicle and requested information. TheEOT character, therefore, has two functions, First, it signifies to thevehicle receiving data from the WCU that new data may be transmittedback to the WCU, and secondly it resets the ID decode for that vehicle.

Generally, then, the WCU should be programmed to serially poll all ofthe vehicles on line to determine which vehicles have information totransmit back thereto. The polling operation may only consist of sendinga vehicle ID, verifying the retransmitted ID, listening for any new datatransmitted by the vehicle and then sending an EOT code, verifying theretransmitted EOT code, and the WCU then increments the ID code to betransmitted and continues the polling operation.

Although the above disclosure has been primarily directed to rollingwarehousing vehicles, it is contemplated that the system will have equalutility and application to any type of vehicle system wherein thevehicles are constrained to travel over predetermined paths. Forexample, the system will have great utility for systems which ride abovea roadway or other passageways on a cushion of air since no physicalcontact of any kind is required between the vehicle and thecommunication medium. Furthermore, the position of the distributedantenna array is not to be limited to locations beneath the vehiclessince in the case of tunneled structures such as subways, etc., themembers of the distributed array could just as well be located in or onthe ceiling or walls of the passage forming means.

It is contemplated that after having read the above disclosures manyalterations and modifications of the present invention will becomeapparent to those of skill in the art. It is therefore to be understoodthat the particular embodiments disclosed are for illustrative purposesonly and are not to be considered limiting to that extent. I, therefore,intend that the appended claims be interpreted as covering all suchadditions and modifications which fall within the true spirit and scopeof the invention.

What is claimed is:

l. A vehicle control system for controlling the operation of awarehousing vehicle and directing its movement over at least twointersecting vehicle paths, comprising:

a first guidance conductor disposed along one of said paths and a secondguidance conductor disposed along the other of said paths;

means for electrically energizing said first and second conductors withsignals of different frequencies to develop a first magnetic guidancefield along said one path and a second magnetic guidance field alongsaid other path;

transmission line extending longitudinally along both said paths andoperative to develop an electro-magnetic communication field along thelength thereof when energized by a first communication signal, saidtransmission line being further operative to conduct a first responsesignal induced therein by an electro-magnetic response field;

a warehouse control unit including first control logic for developingsaid first communication signal and for receiving said first responsesignal; and

a vehicle control unit carried by said vehicle including, a firsttransducer responsive to said communication field and operative todevelop a second communication signal, said first transducer beingadditionally responsive to a second response signal and operative todevelop said electro-magnetic response field, second control logicresponsive to said second communication signal and operative to developa function control signal, a path selection signal and said secondresponse signal, function control means responsive to said functioncontrol signal and operative to control at least one function of saidvehicle, a second transducer responsive to said magnetic guidance fieldand operative to develop guidance signals, and guidance means responsiveto said guidance signals and said path selection signal and operative toguide said vehicle along a selected one of said paths.

2. A vehicle control system for controlling the operation of awarehousing vehicle and for directing its movement over at least twointersecting vehicle paths, comprising:

a guidance conductor disposed along and defining each of saidintersecting vehicle paths and means for electrically energizing eachguidance conductor with a signal of a different frequency to develop adifferent guidance field along each of said paths;

a transmission line extending longitudinally along each of said paths,said transmission line being operative to develop a communication fieldalong the length thereof when energized by a communication signal, andbeing operative to be energized by a response signal induced therein bya response field developed along portions of the length thereof;warehouse control unit including control logic for developing saidcommunication signal and for receiving said response signal; and

a vehicle control unit carried by said vehicle including, receiver meansresponsive to said communication field and said guidance field andoperative to develop guidance signals to guide said vehicle along aselected one of said paths, and transmitter means operative to developsaid response field to communicate data to said warehouse control unit.

3. A vehicle control system in accordance with claim 2 in which saidtransmission line is of twin lead configuration.

4. A vehicle control system in accordance with claim 3 in which saidtwin lead transmission line is terminated into its characteristicimpedance at its distal end.

1. A vehicle control system for controlling the operation of awarehousing vehicle and directing its movement over at least twointersecting vehicle paths, comprising: a first guidance conductordisposed along one of said paths and a second guidance conductordisposed along the other of said paths; means for electricallyenergizing said first and second conductors with signals of differentfrequencies to develop a first magnetic guidance field along said onepath and a second magnetic guidance field along said other path; atransmission line extending longitudinally along both said paths andoperative to develop an electro-magnetic communication field along thelength thereof when energized by a first communication signal, saidtransmission line being further operative to conduct a first responsesignal induced therein by an electro-magnetic response field; awarehouse control unit including first control logic for developing saidfirst communication signal and for receiving said first response signal;and a vehicle control unit carried by said vehicle including, a firsttransducer responsive to said communication field and operative todevelop a second communication signal, said first transducer beingadditionally responsive to a second response signal and operative todevelop said electro-magnetic response field, second control logicresponsive to said second communication signal and operative to developa function control signal, a path selection signal and said secondresponse signal, function control means responsive to said functioncontrol signal and operative to control at least one function of saidvehicle, a second transducer responsive to said magnetic guidance fieldand operative to develop guidance signals, and guidance means responsiveto said guidance signals and said path selection signal and operative toguide said vehicle along a selected one of said paths.
 2. A vehiclecontrol system for controlling the operation of a warehousing vehicleand for directing its movement over at least two intersecting vehiclepaths, comprising: a guidance conductor disposed along and defining eachof said intersecting vehicle paths and means for electrically energizingeach guidance conductor with a signal of a different frequency todevelop a different guidance field along each of said paths; atransmission line extending longitudinally along each of said paths,said transmission line being operative to develop a communication fieldalong the length thereof when energized by a communication signal, andbeing operative to be energized by a response signal induced therein bya response field developed along portions of the length thereof; awarehouse control unit including control logic for developing saidcommunication signal and for receiving said response signal; and avehicle control unit carried by said vehicle including, receiver meansresponsive to said communication field and said guidance field andoperative to develop guidance signals to guide said vehicle along aselected one of said pAths, and transmitter means operative to developsaid response field to communicate data to said warehouse control unit.3. A vehicle control system in accordance with claim 2 in which saidtransmission line is of twin lead configuration.
 4. A vehicle controlsystem in accordance with claim 3 in which said twin lead transmissionline is terminated into its characteristic impedance at its distal end.